CLOTH-POCKETED UNIT
The cloth-pocketed unit consists of many small, light coils, each of which is encased in muslin or burlap. Full-size units of this type usually contain more than 800 individual coils, although the number may vary. In this general classification are mattresses in which the individual coils are not completely encased but are secured at both ends by flat horizontal pockets. In some mattresses of the pocket type the coils are tied together; in others they are not.
CHARACTERIZATION OF A GOOD INNER SPRING
Regardless of its unit construction, an inner-spring mattress of good quality has certain characteristics which can be easily recognized and described. Chief among these are resilience and buoyancy. A mattress with the proper resiliency will give readily when pressure is applied and spring back to its original shape when this pressure is removed. Resilience may be thought of as "plenty of give." Buoyancy is the power to support and sustain the sleeper's weight. A mattress which is buoyant will cradle the body comfortably without letting it sink too deeply into the mattress.
UPHOLSTERY OF INNER-SPRING MATTRESSES
Figure 25.—Convolute coil designed for inner-spring mattress.
The upholstery used to pad the inner-spring unit and give it added comfort conforms in general to that used in solid-filled mattresses.
The most widely used upholstery material is felted cotton. In the better grade mattresses the cotton fiber is of good length, permitting easy felting. In those of lesser quality shorter-fibered cotton is used.
Curled hair makes an excellent but more expensive upholstery material. It is used alone, or in combination with cotton or lamb's wool. Lamb's wool alone or in combination with curled hair is used in the most expensive types. Some manufacturers use lamb's wool on one side for winter use and curled hair on the other for summer.